The present invention relates to means for changing the flow of fluid from longitudinal flow through a longitudinal passage in an element to radial flow through the element; more particularly, to the geometric relationship between intersecting passages for effecting such directional change; and most particularly, to a cylindrical element having longitudinal fluid supply passages intersected by eccentric grooves formed in a surface of the element.
Cam phasers for varying the phase relationship between the pistons and the valves of an internal combustion engine are well known. In some applications, pressurized phaser control oil is supplied from a passage in a camshaft bearing at the rear of the phaser to a fixed oil switching valve mounted on the exterior of the phaser cover at the front of the phaser via one or more first longitudinal passages in a central bolt or plug. The switching valve, on command from an engine control module, supplies oil to, or recovers oil from, opposite-acting timing advance and retard chambers within the phaser. Typically, the switching valve is connected to the chambers via radial passages in a phaser element which communicate with second longitudinal passages in the central plug. Because the angular relationship between the plug and the phaser element may be variable, typically a circumferential oil groove concentric with the plug is formed in the outer surface of the plug at the axial location of the radial passage in the phaser element, giving the phaser element access to the second longitudinal passage regardless of rotation between the plug and the phaser element. In the prior art, the groove and the longitudinal passage in the plug are connected via a radial bore therebetween, which scheme has at least two disadvantages: first, the bore requires separate tooling and machining in forming the plug, thereby increasing cost and complexity; and second, the opening formed into the second passage can be no larger than a bore having a diameter equal to the axial width of the groove, thereby limiting for some applications the maximum oil flow possible.
What is needed is a means for obviating the need for a separate radial bore and a means for increasing the open area between a longitudinal passage and a circumferential groove.
It is a principal object of the present invention to reduce the cost and complexity of manufacturing a cam phaser.
It is a further object of the invention o reduce flow restriction of oil between a longitudinal passage and a circumferential groove.
Briefly described, a cylindrical element formed in accordance with the invention has a first axis and at least one internal, longitudinal passage. A circular circumferential groove, having a second axis and preferably a rectangular cross-section, is formed in an outer surface of the element. The groove axis is parallel to the element axis but is offset radially, making the groove eccentric of the element, such that the groove intersects and breaks through the wall of the longitudinal passage, forming thereby a rectangular opening therebetween. The axial extent of the opening equals the axial width of the groove, and the circumferential extent of the opening is governed by the inter-axial distance.
This effect can be achieved, of course, by a concentric groove rather than eccentric groove. However, when a second longitudinal passage also must be intersected by a second groove, making the second groove also concentric is not readily feasible. The invention, though, using eccentric grooves, makes it easy to accommodate a second passage. The second eccentric groove is spaced apart axially from the first groove and the axis of the second groove is rotationally displaced about the element axis from the first groove, preferably by a large angle, for example 180xc2x0, such that the first eccentric groove does not intersect the second passage, nor does the second eccentric groove intersect the first passage. Greater numbers of passages and grooves are possible, limited by the diameters of the grooves, the positioning of the passages in the element, the diameter of the element, and the depth of the grooves.
In practice, the invention is highly useful in forming a central plug or bolt for a cam phaser for an internal combustion engine wherein oil must be supplied between a switching valve and a phaser element via the plug or bolt.
The invention is also useful in the inverse situation wherein the longitudinal passage (or passages) is formed in an object parallel to a cylindrical bore therein, and the eccentric groove (or grooves) is formed in the wall of the bore.